[Edit] – *You are not using the current version of the theme and the plugin*

Took me a while to realize why nothing is working on my side, since I see you updated your WordPress I assumed plugin was recent as well… I don’t have the version of the theme you are using nor the plugin. Current theme version is 1.7 and you are using 1.3… Please go to themeforest and login using the account you purchased the theme with and download the update please. Be aware that the update will overwrite all theme files including custom.css , so make sure to backup first.

You should ignore what’s below since its only the first part and I ran into problems already since things aren’t matching up.

I wasn’t sure if your sketch was of a page or of an item box. Sounds like the item box. I will give you the instructions, just wanted to make sure I understand you correctly.

I don’t think css alone is a viable solution because css I used wasn’t working correctly on all browsers.

You will also have problems for items on sale because that takes up 70% of each box.

Ok…

1) Please make a backup first before editing any of the files below so that you can revert if something goes wrong.

I would just backup the entire theme wp-content directory and the database (which you should be doing anyways at least once a week automatically). It takes 5 minutes, but if the update goes wrong, you can wind up losing all the time you’ve spent.

Just keep the custom.css file separately, and when you update, don’t do it from WordPress but instead login with ftp, and after backing up, delete the theme folder, and upload the update theme folder right in its place, then replace the custom.css file.

It may also be a good idea for you to start using a child theme so that any customization are done within the child theme and the original isn’t touched.